Meter provers are positive displacement devices that launch pistons in barrels, timing their travel time to deduce the flow rate. Piston travel is typically monitored in only one direction to calibrate or check accuracy of a flow meter. Provers tend to have elaborate hardware to minimize the flow rate measurement errors and are typically intended to calibrate meters used in flow lines greater than four inches in diameter. For smaller lines, the piston meter prover concept has been used to make positive displacement flow meters by providing mechanisms that allow the piston to reciprocate continuously. Reciprocation is facilitated by mechanical linkages that divert valve mechanisms or by electrically operated three or four way diverting valves to achieve piston reciprocation. Often in high pressure hydraulic systems it is desirable to measure flow rates below five gallons per day. For various reasons, a continuous flow measurement may not be required, but a reliable, accurate means tolerant to debris is desirable.